A simple concoction of vodka, ginger beer and lime juice, Moscow Mules have been all the rage for a while now. Much of the hype can be attributed to the pretty copper mugs in which they're traditionally served. But it turns out, the very thing that makes the cocktail so special might also be putting you at risk.

The Iowa Alcoholic Beverages Division issued an advisory bulletin in 2017 explaining the state has joined others in adopting the FDA's Food Code, which says that "copper and copper alloys such as brass may not be used in contact with a food that has a pH below six such as vinegar, fruit juice or wine."

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Since the pH of a standard Moscow Mule falls well below six, the bulletin explains, the copper can leach into the beverage, potentially resulting in food poisoning.

But there's still hope for your favorite drink: "Copper mugs lined on the interior with another metal, such as nickel or stainless steel, are allowed to be used and are widely available," the Iowa Alcoholic Beverages Division clarified.

To be sure your cups are drink-safe, check with the manufacturer of your mugs. If not, look for lined options, like this set of four.

A simple concoction of vodka, ginger beer and lime juice, Moscow Mules have been all the rage for a while now. Much of the hype can be attributed to the pretty copper mugs in which they're traditionally served. But it turns out, the very thing that makes the cocktail so special might also be putting you at risk.